Congestion remained at record-high levels in 2016, with six percent of freeway miles driven affected by traffic congestion. This trend has been driven by worsening conditions at long-standing regional bottlenecks on freeways crisscrossing San Francisco, the East Bay and the South Bay. While past years have seen significant annual growth in congested miles traveled, traffic congestion did not notably get worse in 2016 compared to the previous year, despite a booming economy and corresponding growth in jobs and population. And, as this data makes clear, the effects of regional traffic congestion are more limited in extent than some drivers might think: 94 percent of miles are driven in uncongested conditions.
For the second year in a row, San Francisco topped the list of the region’s counties with the greatest share of miles driven in congestion. At 9.5 percent in 2016, it continues to exceed congestion levels in nearby Alameda County, which has historically been the most congested in the Bay Area. The latest data for these counties, when considered alongside those of neighboring counties, reflect slower freeway speeds and increasing congestion in the urban core. On the other hand, in the more northerly counties of Sonoma, Napa and Solano, drivers spend very little time in congested conditions. These counties have seen little-to-no growth in congestion over the past decade.